Inductive coupling wand having a molded magnetic core

Abstract: An inductive charging system (10) comprises a charging wand (20) that is coupled to a source of power (16) and a charging port (13) that is coupled to a battery (11) of an electric vehicle (12). The charging wand (20) has a magnetic core (21) molded therein.

Description: The present invention relates to a charging device for use in an inductive charging system comprising said charging device coupled to a source of power and insertable into a charging port that is coupled to a battery, said charging device including a magnetic core. The invention relates further to an inductive charging system, comprising a battery, a charging port that is coupled to the battery, a power source, and a charging device that is coupled to the power source and insertable into the charging port for charging the battery. Such a charging device and such an inductive charging system are known from EP-A-0 552 737. The present invention relates generally to inductive chargers for use in charging electric vehicles, and more particularly, to inductive chargers having magnetic cores molded into charging wands thereof. Charging wands or couplers are employed as part of an inductive charging system and are used to charge batteries in electric vehicles. The inductive charging system comprises the charging wand and a charging port. The charging wand is a hand-held device that includes a magnetic core having a primary winding disposed in proximity thereto. The charging port is a device that is part of the vehicle and includes secondary cores and secondary windings that are coupled to the battery of the vehicle. The primary winding is coupled to a source of power and when the wand is inserted into the charging port, power is coupled from the power source to the battery of the electric vehicle. Heretofore, the charging wands have been fabricated such that it has been necessary to machine the side walls of the magnetic core prior to assembly. It has also been necessary to machine the cores to exact tolerances, because core dimensions can vary by as much as 2% depending on the core mixture that is used. For example, a 5.08 cm [2 inch] diameter core has an overall tolerance zone of about 0.10 cm [0.04 inches]. To accurately machine the core to a tolerance of +0.010 increases the unit cost by 100%. GB-A-1 025 448 discloses an inductive signal transfer device. This transfer device is used in combination with an oxygen supply connection to a mask or helmet in a unitary quick disconnect arrangement which avoids the use of metal-to-metal contacts. The inductive signal transfer device includes an inductive electrical plug and a socket connector comprising a plurality of closed loop transformer cores, each of which is split into two halves. The two halves of the transformer cores are mounted in the plug and socket parts of the connector respectively with their ends adjacent surfaces of these parts. The assembled core halves are, together with their respective windings, embedded in plastic blocks which are placed in pockets in the plug and the socket, respectively. Further, US-A-3,418,552 discloses a battery charger for an electric toothbrush. The charger includes a steel receptacle into which the bottom of the electric toothbrush is to be inserted. Further, an insert which is formed by molding a primary winding within a suitable encapsulating material is placed within the receptacle. A stud made of metal is inserted into a central opening in the insert and projects therefrom so as to be received by a corresponding central opening in the bottom of the housing of the electric toothbrush. The stud may be molded into the insert. The transformer core of the charger is formed by the stud and the receptacle. The toothbrush itself does not contain any core elements but only a secondary winding. It is the object of the present invention to provide for an improved charging device and an improved inductive charging system whereby the requirement for machining the side walls of the magnetic core prior to assembly and the need to machine the core to exact tolerances is eliminated. This object is achieved by a charging device, mentioned at the outset, wherein the charging device has said magnetic core molded into a surrounding member, the surrounding member being secured to the body of the charging device, and that a primary winding is diposed in the body and adapt to carry current derived from the power source coupled thereto, wherein the surrounding member is molded around the periphery of the magnetic core and secured to the body in proximity to the primary winding. The above object is further achieved by an inductive charging system, mentioned at the outset, comprising such a charging device. Generally, in order to provide for the above and other objectives, the present invention comprises an inductive charging system comprising a charging wand that is coupled to a source of power and a charging port that is coupled to a battery of an electric vehicle. The improvement provided by the present invention is a charging wand having a magnetic core molded therein. The magnetic core is molded into a surrounding plastic disk, ring, or sleeve which in turn is secured into the body of the charging wand. The present invention improves the assembly process for charging wands by eliminating the wide tolerance range associated with magnetic core fabrication. The present invention employs an injection molding method similar to those that mold metal inserts directly into a plastic part. In the present invention, no concern is given to the size of the magnetic core other than to provide sufficient plastic wall thickness to prevent pullout from the body of the wand when it is secured therein. Molding the magnetic cores into the inductive charge wand eliminates the requirement for machining the side walls of the magnetic cores. By molding a ring around the core and securing the molded assembly into the wand results in substantial cost savings by eliminating the need to machine the cores to exact tolerances. The various features and advantages of the present invention may be more readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: Fig. 1 illustrates a charging system for use in charging a battery of an electric vehicle that comprises an inductive charging wand having a magnetic core directly molded therein, not belonging to the present invention; Figs. 2a and 2b illustrate cross sectional views of embodiments of a magnetic core molded into a plastic ring that may be employed in the inductive charging wand of Fig. 1; and Fig. 3 illustrates the magnetic core of Fig. 2a secured into a charging wand. Referring to the drawing figures, Fig. 1 illustrates a charging system 10 for use in charging a battery 11 of an electric vehicle 12 that comprises an inductive charging wand 20 having a magnetic core 21 directly molded therein not belonging to the present invention. The magnetic core 21 may be comprised of ferrite material, for example. The inductive charging system 10 comprises the charging wand 20 and a charging port 13. The charging port 13 is comprised of secondary magnetic cores 14, and secondary windings 15 that are coupled to the battery 11 of the electric vehicle 12, for example. The charging wand 20 is coupled to a power source 16. The charging wand 20 is comprised of a body 22 having a handle 23 for gripping by a user. The body 22 is typically made of a plastic material such as glass filled polyester-type plastic, for example. The charging wand 20 includes a primary winding 30 that is electrically coupled to the power source 16 that is adapted to couple power to the battery 11 of the vehicle 12 by way of the charging port 13 and charging wand 20 when the charging wand 20 is inserted into the charging port 13. The improvement provided by the present invention is that the charging wand 20 is designed such that its magnetic core 21 is molded into a plastic disk, ring, or sleeve 24 that surrounds the magnetic core 21 and which in turn is secured into the body 22 of the charging wand 20. Figs. 2a and 2b illustrate cross sectional views of embodiments of a magnetic core 21 molded into a plastic ring 24 that may be employed in the inductive charging wand 20 of Fig. 1 Fig. 2a illustrates the magnetic core 21 molded into the plastic ring 24. Fig. 2b shows the core 21 molded into a plastic ring 24 that has a groove 28 that mates with a lip 29 formed along the edge of an opening 26 in the body 22 of the wand 20 to secure the core 21 into the body 22. Fig. 3 illustrates the magnetic core 21 shown in Fig. 2a secured into the charging wand 20 by means of adhesive 27. In view of the above, it should be appreciated that there are two aspects. The first is to mold the magnetic core 21 directly in the inductive charging wand 20, not belonging to the invention. The second is to mold the plastic ring 24 around the magnetic core 21 to form a molded core/ring assembly 25 and then secure the core/ring assembly 25 into the body 22 of the charging wand 20, in accordance with the present invention. Molding the magnetic core 21 directly into the inductive charging wand 20 requires that the wand 20 is ready for final assembly. To fabricate such a wand 20, the component pieces of the charging wand 20 are assembled and placed into a molding fixture. Then the magnetic core 21 is placed into the molding fixture and secured or indexed in a manner that prevents it for moving relative to the wand 20 during the molding process. The molding fixture is closed and mold material (plastic) is poured or injected into cavities in the molding fixture. After curing, the molded and assembled charging wand 20 is removed from the molding fixture and the fabricated wand 20 has the magnetic core 21 molded into its body 22. The second aspect, in accordance with the present invention, is to mold the plastic ring 24 around the periphery of the magnetic core 21 and then install the core/ring assembly 25 into the opening 26 formed in the charging wand 20. The outer periphery of the ring 24 may be held to a very accurate dimension that is set by the mold dimensions. This provides for controlled and repeatable assembly of the core/ring assembly 25 into the opening 26 in the body 22 of the charging wand 20. Securing the core/ring assembly 25 into the charging wand 20 may be accomplished by using the adhesive 27 to hold the core/ring assembly 25 in place, as shown in Figs. 2 & 3. Typically, an adhesive 27 such as epoxy, or silicone, for example, may be employed to secure the core/ring assembly 25 in the charging wand 20. The present invention may be employed in devices that provide for rapid, high rate charging of batteries or electric vehicle batteries 11, and that provide for power transfer between installations employing batteries 11, and the like.

Claims: A charging device (20) for use in an inductive charging system (10) comprising said charging device (20) coupled to a source of power (16) and insertable into a charging port (13) that is coupled to a battery (11), said charging device (20) including a magnetic core (21), characterized in that said charging device (20) has said magnetic core (21) molded into a surrounding member (24), the surrounding member (24) being secured to the body (22) of the charging device (20), and that a primary winding (30) is disposed in the body (22) and adapted to carry current derived from the power source (16) coupled thereto, wherein the surrounding member (24) is molded around the periphery of the magnetic core (21) and secured to the body (22) in proximity to the primary winding (30). The charging device of claim 1, characterized in that the surrounding member (24) is secured to the body (22) of the charging device (20) by means of adhesive (27). The charging device of claim 2, characterized in that the adhesive (27) comprises epoxy. The charging device of any of claims 1 - 3, characterized in that the surrounding member (24) has a groove (28) that mates with a lip (29) formed along the edge of an opening (26) in the body (22) of the charging device (20). The charging device of any of claims 1 - 4, characterized in that said battery (11) is a battery (11) of an electric vehicle (12). An inductive charging system (10), comprising: a battery (11); a charging port (13) that is coupled to the battery (11); a power source (16); and a charging device (20) that is coupled to the power source (16) and is insertable into the charging port (13) for charging the battery (11), characterized in that the charging device (20) is the charging device (20) of any of claims 1 - 5.

Inventors: ABBOTT RUSSELL M, QUON WILLIAM, ABBOTT, RUSSELL M., QUON, WILLIAM
Applicants: HUGHES AIRCRAFT CO, HUGHES AIRCRAFT COMPANY
Application year: 1994
Main classification: H01F38
IPC codes: H01F38, H02J7, H01F27, B60L11, H02J17